1. Field of the Invention
The invention relates to a surface treatment that imparts hydrophilicity.
2. Description of Related Art
A treatment of imparting hydrophilicity is carried out in various industrial fields. There is generally adopted a method in which oxygen is activated to generate ozone through the use of an energy wave, for example, ultraviolet light and a hydrophilic group is formed on a surface to be treated through the use of the ozone (Japanese Patent Application Publication No. 2012-200622 (JP-2012-200622 A)).
By the way, as for a fuel cell that employs a polymer electrolyte membrane (hereinafter referred to simply as “an electrolyte membrane”) as an electrolyte, there is known a configuration in which a membrane electrode assembly that is obtained by joining electrode catalytic layers to both faces of the electrolyte membrane is sandwiched by separators. A gas that is supplied to the electrode catalytic layer flows through one face of each of the separators (this face will be referred to also as a gas face), and a cooling medium for cooling the fuel cell flows through the other face of each of the separators (this face will be referred to also as a cooling face). In each of these separators, the gas face is required to exhibit hydrophilicity in order to discharge the water produced through the generation of electric power by the fuel cell to the outside of the fuel cell. On the other hand, when cells are laminated and fastened, a gasket is glued to the cooling face so as to prevent reactive gas and coolant from leaking out. Therefore, the cooling face is required to exhibit hydrophilicity in order to enhance the adhesiveness.
With the surface treatment apparatus of Japanese Patent Application Publication No. 2012-200622 (JP-2012-200622 A), only one face of each of the separators can be subjected to a hydrophilization treatment. Therefore, in the case where both faces of each of the separators is subjected to the hydrophilization treatment, one of the faces is subjected to the hydrophilization treatment, and then the other face is subjected to the hydrophilization treatment. For this reason, a large quantity of labor and a long time are needed to carry out the treatment. Thus, there have been demands for a technology that makes it possible to reduce the quantity of labor and time for the hydrophilization treatment in the case where both the faces of each of the separators is subjected to the treatment. This technology has been desired not only for fuel cell separators but also for surface treatment apparatuses for treating various workpieces in common. Moreover, a reduction in cost, the saving of resources, the facilitation of manufacture, the enhancement of performance and the like have been desired in conventional surface treatment apparatuses.